A virtual hard disk crashed containing our sql server and exchange server. I have several backups but the one I can use is 3weeks old. What happens to local Outlook clients when I restore that Hyper-v backup? Will all email from the clients from the last 3 weeks by deleted during sync?
Interesting question. I've never dealt with it directly (restoring that far back) to care what happens to the OST files, so I found this article online: http://searchexchange.techtarget.com/answer/What-happens-to-ost-files-after-restoring-an-Exchange-backup
To sum up what Brien thinks would happen:
However, I'm not sure I agree with him on this one...since his test is removing email in OWA and the server is still online. So the server KNOWS that the email was deleted.
I tend to agree with this here: http://social.technet.microsoft.com/Forums/office/en-US/89be9383-6efa-400e-9978-db13b88313f6/what-happens-to-ost-files-when-an-old-exchange-backup-is-restored?forum=exchangesvravailabilityandisasterrecoverylegacy
where the OP themselves stated:
There it seems more likely...that the OST file has emails that are NEWER than what Exchange knows about and then syncs them BACK to the Exchange mailbox store.
An example TEST for this would be easy enough.
BTW, I just did this test myself and it works...
HOWEVER, IF you are the least bit skeptical, I would create an exported PST file on each user's Outlook first of their OST file (at a minimum grabbing the last 3 weeks worth but easier would be the entire OST). This I would probably do regardless for anyone that is a VIP...better safe than sorry with them.
BUT TO SUM UP MY ANSWER:
In my test I show that the email in the OST file should be there. I would still recommend backing up the local OST files to PST's first if you have the resources to do so. The main reason I state this is because I'm not certain the existing OST file will be the one used by Outlook after the restore completes or if the sync will suddenly cause the server to want to create a new one. If it does you technically won't lose the old OST file, but you would need 3rd party tools at that point to extract email from them or convert them to PST.
protected by Community♦ Sep 11 '14 at 12:45
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